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Mineral Resources > Online Spatial Data > Geology > by state > Wyoming Geology

Geologic units in Carbon county, Wyoming

[Additional scientific data in this geographic area]

Quartz diorite (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area

QUARTZ DIORITE. Sierra Madre--Encampment River Granodiorite 4; age 1,800 Ma. Medicine Bow Mountains--Keystone Quartz Diorite 5. Hartville uplift--Diorite of Twin Hills 6.

Lithology: quartz diorite

Hanna Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 5 % of this area

HANNA FORMATION--Brown and gray sandstone, shale, conglomerate, and coal; giant quartzite boulders near Medicine Bow Mountains.

Lithology: medium-grained mixed clastic; fine-grained mixed clastic; conglomerate; coal

Frontier Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.8 % of this area

FRONTIER FORMATION in thrust belt--White to brown sandstone and dark-gray shale; oyster coquina in upper part; coal and lignite in lower part; in north and south Wyoming--Gray sandstone and sandy shale.

Lithology: sandstone; shale; coal

Green River Formation: Laney Member (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.7 % of this area

GREEN RIVER FORMATION Laney Member (age probably about 45 Ma)--Oil shale and marlstone.

Lithology: oil shale; mixed clastic/carbonate

Upper Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Late) at surface, covers 5 % of this area

UPPER MIOCENE ROCKS--Southwest Wyoming: South end of Wind River Range--Siliceous, arkosic, and locally radioactive sandstone, claystone, and conglomerate. Fission-track age about 27 Ma. Recent work suggests that part of these deposits may be of Eocene age. Pliocene and Miocene (as originally defined 2) South Pass Formation. Saratoga Valley--White to greenish-gray tuffaceous sandstone, siltstone, and claystone; locally conglomeratic. North Park Formation; Central Wyoming: Arkosic sandstone, conglomerate, and siltstone; some light-colored tuffaceous radioactive claystone and white cherty limestone. North of Sweetwater River in Granite Mountains--Light-colored tuffaceous radioactive claystone, siltstone, sandstone, and arkose. Moonstone Formation; East Wyoming: Light-colored tuffaceous claystone, sandstone, and conglomerate. Ogallala Formation in Denver Basin.

Lithology: sandstone; claystone; conglomerate; siltstone; limestone

Green River Formation: Tipton Shale Member or Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area

GREEN RIVER FORMATION Tipton Shale Member or Tongue--Oil shale and marlstone.

Lithology: oil shale; mixed clastic/carbonate

Battle Spring Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area

BATTLE SPRING FORMATION--Equivalent to, and lithologically similar to locally derived basin-margin conglomerate of Wasatch Formation; merges southward into main body of Wasatch Formation. Lower part is Paleocene.

Lithology: conglomerate

Steele Shale and Niobrara Formations (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % of this area

STEELE SHALE (Ks) AND NIOBRARA FORMATIONS (Kn). STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone. NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale.

Lithology: shale; mixed clastic/volcanic; mixed clastic/carbonate; sandstone

Playa lake and other lacustrine deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

PLAYA LAKE AND OTHER LACUSTRINE DEPOSITS--Chiefly clay, silt, and fine sand. Includes travertine deposits.

Lithology: playa; lake or marine deposit (non-glacial)

Gallatin Limestone, Gros Ventre Formation and equivalents, and Flathead Sandstone (N) or Cambrian Rocks (S) (Phanerozoic | Paleozoic | Cambrian-Middle Cambrian-Furongian) at surface, covers < 0.1 % of this area

GALLATIN LIMESTONE, GROS VENTRE FORMATION and equivalents, and FLATHEAD SANDSTONE (north Wyoming). GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. CAMBRIAN ROCKS (south Wyoming). South flank of Granite Mountains--Blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at base. On and south of Rawlins uplift--Glauconitic quartzitic sandstone.

Lithology: limestone; sandstone; shale

Cloverly and Morrison Formations (N,S) or Cloverly Formation, Inyan Kara Group, and Morrison Formation (Phanerozoic | Mesozoic | Jurassic-Late Cretaceous-Early) at surface, covers 0.1 % of this area

CLOVERLY FORMATION and MORRISON FORMATION. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable; CLOVERLY FORMATION (Hartville uplift) or INYAN KARA GROUP (Black Hills) and MORRISON FORMATION. CLOVERLY FORMATION--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. INYAN KARA GROUP--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. Includes Fall River and Lakota Formations. MORRISON FORMATION, in northeast Wyoming, dully variegated siliceous claystone, nodular white limestone, and gray silty sandstone.

Lithology: sandstone; claystone; conglomerate; limestone

Wells and Amsden Formations (TB), or Casper Formation and Madison Limestone (N, S) (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early Pennsylvanian-Middle(?) Pennsylvanian-Late(?) Permian) at surface, covers 0.2 % of this area

WELLS AND AMSDEN FORMATIONS (Thrust Belt). WELLS FORMATION--Gray limestone interbedded with yellow limy sandstone. AMSDEN FORMATION--Red and gray cherty limestone and shale, sandstone, and conglomerate. CASPER FORMATION AND MADISON LIMESTONE (north, south Wyoming). CASPER FORMATION--Gray, tan, and red thick-bedded sandstone underlain by interbedded sandstone and pink and gray limestone. May include some Devonian(?) sandstone along east flank of Laramie Mountains. MADISON LIMESTONE--Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite).

Lithology: limestone; sandstone; shale; conglomerate; dolostone (dolomite)

Frontier Formation and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers 0.6 % of this area

FRONTIER FORMATION (Kf) AND MOWRY (Kmr) AND THERMOPOLIS SHALES. FRONTIER FORMATION--Gray sandstone and sandy shale. In Northern Yellowstone area, Yellowish- to medium-gray sandstone; tuffaceous and carbonaceous in lower part. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.

Lithology: sandstone; shale; mixed clastic/volcanic

Granitic rocks (Archean) at surface, covers 3 % of this area

GRANITIC ROCKS OF 2,600-Ma AGE GROUP. Teton Range--Mount Owen Quartz Monzonite. Age 2,500+/- Ma; may be of Early Proterozoic age. Gros Ventre and Washakie Ranges--Granitic rocks. Yellowstone National Park, Owl Creek, Granite, and Seminoe Mountains, Rawlins uplift, and Medicine Bow Mountains--Granite. Wind River Range--Granodiorite to porphyritic and equigranular granite. Sierra Madre--Granite and granodiorite. Laramie Mountains--Granite, amphibolite, and minor amounts of metasedimentary rocks. Hartville uplift--Granite and quartz monzonite. Black Hills uplift--Granite and minor amounts of metasedimentary rocks.

Lithology: granitoid

Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.5 % of this area

MOWRY (Kmr) AND THERMOPOLIS SHALES. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.

Lithology: shale; sandstone; mixed clastic/volcanic

Steele Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 5 % of this area

STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone.

Lithology: shale; mixed clastic/volcanic; sandstone

Ferris Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers 2 % of this area

FERRIS FORMATION--Brown and gray sandstone and shale; sparse carbonaceous shale and coal beds; thin lenses of pebble conglomerate.

Lithology: sandstone; shale; coal; conglomerate

Metasedimentary rocks: Deep Lake Group (Proterozoic | Paleoproterozoic ) at surface, covers 0.9 % of this area

METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Deep Lake Group 3--Quartzite, diamictite, pelitic schist, and quartz-pebble conglomerate.

Lithology: metasedimentary rock

Wind River Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 3 % of this area

WIND RIVER FORMATION Northwest Wyoming (Jackson Hole)--Variegated red and white claystone and siltstone; largely nontuffaceous except near the top; lenticular coal unit in middle. At base locally includes equivalent of Indian Meadows Formation; Central Wyoming--Variegated claystone and sandstone; lenticular conglomerate. Age of tuff at top 49 Ma.

Lithology: claystone; siltstone; sandstone; coal

Granite gneiss (Archean) at surface, covers 3 % of this area

GRANITE GNEISS (AGE 2,600 TO 3,100+ Ma)--Layered to massive, locally migmatitic; metasedimentary and metavolcanic rocks locally common. Includes Webb Canyon Gneiss in Teton Range.

Lithology: granitic gneiss

Conglomerate (Phanerozoic | Cenozoic | Tertiary Quaternary | Miocene Pliocene(?) Pleistocene) at surface, covers < 0.1 % of this area

CONGLOMERATE--Northwest Wyoming (Jackson Hole) (Pleistocene or Pliocene)--Paleozoic clasts, chiefly of Madison Limestone, in a lithified carbonate matrix; Central (Medicine Bow Mountains) and east Wyoming (east of Laramie Mountains) (Pleistocene to Miocene)--Giant granite boulders in an arkose matrix.

Lithology: conglomerate

White River Formation--Upper conglomerate member (Phanerozoic | Cenozoic | Tertiary | Oligocene ) at surface, covers 1.0 % of this area

WHITE RIVER FORMATION Upper conglomerate member--Light-gray soft conglomeratic tuffaceous sandstone and conglomerate of Precambrian clasts.

Lithology: medium-grained mixed clastic; conglomerate; mixed clastic/volcanic

White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers 1.0 % of this area

WHITE RIVER FORMATION (AGE 31 TO 35 Ma)--White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.

Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic

Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 2 % of this area

WASATCH FORMATION Cathedral Bluffs Tongue--Variegated claystone and lenticular sandstone; conglomeratic near south margin of Wind River Range.

Lithology: fine-grained mixed clastic; medium-grained mixed clastic

Lance Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % of this area

LANCE FORMATION north Wyoming--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses; south and northeast Wyoming--Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.

Lithology: sandstone; shale; conglomerate; coal

Granitic rocks (Proterozoic | Paleoproterozoic ) at surface, covers 1 % of this area

GRANITIC ROCKS OF 1,700-Ma AGE GROUP.

Lithology: granitoid

Lower Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Early) at surface, covers < 0.1 % of this area

LOWER MIOCENE ROCKS--Northwest Wyoming (Bighorn Mountains): Gray soft poorly bedded to massive sandstone; Central Wyoming: Tuffaceous sandstone, siltstone, and white marl.

Lithology: sandstone; siltstone

Cody Shale and Frontier Formation (N, S) (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers < 0.1 % of this area

CODY SHALE AND FRONTIER FORMATION north and south Wyoming. CODY SHALE (AGE 78 TO 83 Ma) (Kc2)--Dull-gray shale, gray siltstone, and fine-grained gray sandstone. FRONTIER FORMATION (Kf2)--Gray sandstone and sandy shale.

Lithology: mudstone; sandstone

Cloverly, Morrison, and Sundance Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.9 % of this area

CLOVERLY, MORRISON, AND SUNDANCE (Js) FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.

Lithology: fine-grained mixed clastic; medium-grained mixed clastic; limestone; mixed clastic/volcanic; conglomerate

Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers 14 % of this area

MIOCENE ROCKS--Southwest Wyoming: Southern Rock Springs uplift--Pale-green to tan tuffaceous sandstone and claystone of Miocene(?) age. Conglomerate of uncertain correlation locally at base. Saratoga Valley and west and southwest to Colorado--White massive soft tuffaceous sandstone and lesser amounts of white marl; lower part conglomeratic. Underlies North Park Formation in Saratoga Valley. To the west and southwest is called Browns Park Formation. Rawlins area--White massive soft tuffaceous sandstone; Central Wyoming: White soft tuffaceous sandstone. Locally derived conglomerate in upper and lower parts of sequence; in places lower conglomeratic sequence may be of Oligocene age. In Granite Mountains K/Ar age of tuff in lower part of sandstone sequence about 17 Ma and fission-track age of lower conglomerate about 24 Ma.

Lithology: sandstone; conglomerate; claystone

Medicine Bow Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 2 % of this area

MEDICINE BOW FORMATION--Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.

Lithology: sandstone; shale; coal

Madison Limestone, Darby Formation, Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone (N), Madison Limestone and Cambrian rocks (S), Minnekahta Limestone, Opeche Shale, Minnelusa Formation, Pahasapa and Englewood Limestones, Whitewood Dolomite, Winnipeg and Deadwood Formations (NE), or Paleozoic, undifferentiated (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous(?) Permian) at surface, covers 0.2 % of this area

MADISON LIMESTONE, DARBY FORMATION, BIGHORN DOLOMITE, GALLATIN LIMESTONE, GROS VENTRE FORMATION, AND FLATHEAD SANDSTONE (north Wyoming). MADISON LIMESTONE OR GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). DARBY FORMATION--Yellow and greenish-gray shale and dolomitic siltstone underlain by fetid brown dolomite and limestone. BIGHORN DOLOMITE--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. MADISON LIMESTONE AND CAMBRIAN ROCKS (south Wyoming). MADISON LIMESTONE--Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). CAMBRIAN ROCKS--On south flank of Granite Mountains, blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at bae. On and south of Rawlins uplift, glauconitic quartzitic sandstone. MINNEKAHTA LIMESTONE, OPECHE SHALE, MINNELUSA FORMATION, PAHASAPA AND ENGLEWOOD LIMESTONES, WHITEWOOD DOLOMITE, AND WINNIPEG AND DEADWOOD FORMATIONS--Various combinations (northeast Wyoming). MINNEKAHTA LIMESTONE--Gray slabby hard limestone. Locally is a member of the Goose Egg Formation. OPECHE SHALE--Red soft sandy shale. Locally is a member of the Goose Egg Formation. MINNELUSA FORMATION--Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum. PAHASAPA LIMESTONE--Gray massive dolomititc limestone. ENGLEWOOD LIMESTONE--Pink slabby dolomitic limestone. WHITEWOOD DOLOMITE--Buff massive fossiliferous dolomite. WINNIPEG FORMATION--Pink to yellow siltstone and shale. DEADWOOD FORMATION--Red and brown quartzitic sandstone. PALEOZOIC ROCKS, undifferentiated (Thrust Belt).

Lithology: limestone; dolostone (dolomite); shale; sandstone; siltstone

Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % of this area

NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale.

Lithology: limestone; fine-grained mixed clastic

Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 5 % of this area

LEWIS SHALE (AGE ABOUT 68 Ma)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Lithology: shale; sandstone

Madison Limestone or Group (S) (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early Mississippian-Middle(?) Mississippian-Late) at surface, covers 0.2 % of this area

MADISON LIMESTONE OR GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite).

Lithology: limestone; dolostone (dolomite)

Fox Hills Sandstone and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

FOX HILLS SANDSTONE AND LEWIS SHALE. FOX HILLS SANDSTONE (Kfh)--Light-colored sandstone and gray sandy shale containing marine fossils. LEWIS SHALE (AGE ABOUT 68 Ma) (Kle)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Lithology: sandstone; shale

Metasedimentary and metavolcanic rocks (Archean) at surface, covers 0.8 % of this area

METASEDIMENTARY AND METAVOLCANIC ROCKS--Amphibolite, hornblende gneiss, biotite gneiss, quartzite, iron-formation, metaconglomerate, marble, and pelitic schist; locally preserved textures and structures suggest origin to be sedimentary or volcanic. Older than 2,875 Ma in Teton Range; older than 3,200 Ma in Granite Mountains; older than 2,600 Ma in Medicine Bow Mountains and Sierra Madre, where it is the Late Archean Phantom Lake Metamorphic Suite 3.

Lithology: metasedimentary rock; metavolcanic rock

Washakie Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (43-44 Ma)) at surface, covers < 0.1 % of this area

WASHAKIE FORMATION (AGE ABOUT 43 TO 44 Ma)--Gray, green, tan, and dull-red tuffaceous arkosic sandstone and claystone.

Lithology: medium-grained mixed clastic; mixed clastic/volcanic

Basalt flows and intrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area

BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS (AGE ABOUT 11 Ma).

Lithology: basalt

Dune sand and loess (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 4 % of this area

DUNE SAND AND LOESS--Includes active and dormant sand dunes. In northwestern Wyoming is chiefly loess (age 12,000-19,000 years).

Lithology: dune sand; loess

Metasedimentary rocks: Libby Creek Group (Proterozoic | Paleoproterozoic ) at surface, covers 0.5 % of this area

METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Libby Creek Group 3--Pelitic schist, amphibole schist, quartzite, diamictite, quartz-pebble conglomerate, and marble.

Lithology: metasedimentary rock

Metasedimentary and metavolcanic rocks (Proterozoic | Paleoproterozoic ) at surface, covers 2 % of this area

METASEDIMENTARY AND METAVOLCANIC ROCKS. Sierra Madre--Granite gneiss, felsic gneiss, amphibolite, and metavolcanic rocks. Medicine Bow Mountains--Granite gneiss, felsic gneiss, amphibolite, and hornblende gneiss. Laramie Mountains--Pelitic schist, marble, granite gneiss, layered amphibolite, and felsic gneiss. Black Hills--Pelitic schist; includes minor amounts of granite and amphibolite.

Lithology: metasedimentary rock; metavolcanic rock

Sundance Formation (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers < 0.1 % of this area

SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.

Lithology: sandstone; shale

Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 2 % of this area

WASATCH FORMATION Main body--Drab sandstone, drab to variegated claystone and siltstone; locally derived conglomerate around basin margins. Lower part is Paleocene.

Lithology: sandstone; fine-grained mixed clastic; conglomerate

Sandstone and Conglomerate (Phanerozoic | Cenozoic | Tertiary | Oligocene Miocene) at surface, covers < 0.1 % of this area

SANDSTONE AND CONGLOMERATE--Gray hard coarse-grained sandstone and conglomerate.

Lithology: sandstone; conglomerate

Peridotite intrusive rocks (Archean) at surface, covers < 0.1 % of this area

PERIDOTITE INTRUSIVE ROCKS--In Laramie Mountains.

Lithology: peridotite

Landslide deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.5 % of this area

LANDSLIDE DEPOSITS--Locally includes intermixed landslide and glacial deposits, talus, and rock-glacier deposits.

Lithology: landslide; glacial drift

Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % of this area

GRAVEL, PEDIMENT, AND FAN DEPOSITS--Mostly locally derived clasts. Includes some glacial deposits along east flank of Wind River Range. Locally includes some Tertiary gravels.

Lithology: unconsolidated deposit

Shear zone (Archean) at surface, covers 0.2 % of this area

Lithology: tectonite

Glacial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % of this area

GLACIAL DEPOSITS--Till and outwash of sand, gravel, and boulders.

Lithology: glacial drift

Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 3 % of this area

FORT UNION FORMATION northwest, southwest, and central Wyoming--Brown to gray sandstone, gray to black shale, and thin coal beds; east Wyoming--Light-colored massive sandstone, drab shale, and thick coal beds.

Lithology: sandstone; shale; coal

Mafic intrusive rocks (Archean) at surface, covers 0.2 % of this area

MAFIC INTRUSIVE ROCKS.

Lithology: plutonic rock (phaneritic)

Mesaverde Formation (N) or Mesaverde Group (S) (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 8 % of this area

MESAVERDE FORMATION (north Wyoming)--Light-colored massive to thin-bedded sandstone, gray sandy shale, and coal beds. In Jackson Hole locally contains gold-bearing quartzite conglomerate. North of North Fork Powder River east of the Bighorn Mountains, consists solely of the Parkman Sandstone Member; MESAVERDE GROUP (SOUTH WYOMING). Includes Almond Formation, Ericson Sandstone, Rock Springs and Blair Formations in Rock Springs uplift; Almond Formation (white and brown soft sandstone, gray sandy shale, coal and carbonaceous shale), Pine Ridge Sandstone (light-gray sandstone and thin coal beds), and Allen Ridge (gray sandstone, shale, and thin coal beds) and Haystack Mountains (gray marine sandstone and shale) Formations in Rawlins uplift; Pine Ridge Sandstone (light-gray sandstone and thin coal beds) and Rock River Formation (soft sandstone and sandy shale) in Laramie Basin.

Lithology: sandstone; shale; coal; conglomerate

Undivided surficial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

UNDIVIDED SURFICIAL DEPOSITS--Mostly alluvium, colluvium, and glacial and landslide deposits. Primarily in Yellowstone area and Bighorn Mountains.

Lithology: alluvium; colluvium; glacial drift; landslide

Wagon Bed Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (45-49 Ma)) at surface, covers 0.2 % of this area

WAGON BED FORMATION (AGE ABOUT 45 TO 49 Ma)--Southwest and central Wyoming--Green and gray tuffaceous claystone, sandstone, and conglomerate; some uranium-phosphate marlstone and variegated bentonitic claystone. Locally contains oil shale between Wind River and Bighorn Basins; Central Wyoming (west side of Laramie Mountains)--Dull-green siliceous bentonitic claystone and tuff; giant granite boulder conglomerate in tuffaceous matrix.

Lithology: claystone; conglomerate; sandstone

Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 8 % of this area

ALLUVIUM AND COLLUVIUM--Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.

Lithology: alluvium; colluvium

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils.

Lithology: sandstone; shale

Goose Egg Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early) at surface, covers 0.6 % of this area

GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.

Lithology: mudstone; carbonate; evaporite; dolostone (dolomite)

Green River Formation: Luman Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area

GREEN RIVER FORMATION Luman Tongue--Oil shale, carbonaceous shale, and sandstone.

Lithology: fine-grained mixed clastic; oil shale

Mafic intrusive rocks (Proterozoic | Paleoproterozoic ) at surface, covers 0.7 % of this area

MAFIC INTRUSIVE ROCKS. Sierra Madre--Gabbro of Elkhorn Mountain; age 1,800 Ma. Medicine Bow Mountains--Mullen Creek 5 and Lake Owens 7 Mafic Complexes; older than 1,700 Ma.

Lithology: gabbroid

Tensleep Sandstone and Amsden Formation (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian) at surface, covers 0.8 % of this area

TENSLEEP SANDSTONE AND AMSDEN FORMATION. North Wyoming: TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. Permian fossils have been found in the topmost beds of the Tensleep at some localities in Washakie Range, Owl Creek Mountains, and southern Bighorn Mountains. AMSDEN FORMATION--Red and green shale and dolomite; at base is brown sandstone. South Wyoming: TENSLEEP SANDSTONE AND AMSDEN FORMATION. TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. AMSDEN FORMATION--Red and green shale and dolomite; at base is persistent red to brown sandstone.

Lithology: sandstone; carbonate; shale

Chugwater Formation (N, NE), or Chugwater Formation or Group (S) (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers 0.8 % of this area

CHUGWATER FORMATION (north, northeast Wyoming)--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. [None mapped in the NE]; CHUGWATER FORMATION OR GROUP (south Wyomingt)--Red shale and siltstone containing thin gypsum partings near base. Group includes Popo Agie Formation (red shale and red, yellow, and purple siltstone; lenses of lime-pellet conglomerate), Crow Mountain Sandstone (red and gray, thick bedded), Alcova Limestone, and Red Peak Formation (red siltstone and shale). Chugwater Formation includes as members all the units listed above. Includes overlying Jelm Formation in Shirley and Seminoe Mountains and at northern end of Laramie Basin. JELM FORMATION--Red sandstone.

Lithology: siltstone; shale; sandstone; limestone; conglomerate

Metasedimentary rocks (Archean) at surface, covers < 0.1 % of this area

METASEDIMENTARY ROCKS. Wind River Range--Metagraywacke, pelitic schist, metaconglomerate, graphitic schist, and iron-formation; local meta-andesite. At least 2,800 Ma. Seminoe Mountains (southeast end of Granite Mountains)--Pelitic schist, quartzite, and iron-formation. Casper Mountain (northwest extension of Laramie Mountains)--Felsic gneiss, quartzite, and iron-formation. Laramie Mountains--Pelitic schist, iron-formation, quartzite, marble, metaconglomerate, and metagraywacke.

Lithology: metasedimentary rock

Cody Shale (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers 0.5 % of this area

CODY SHALE (AGE 78 TO 83 Ma) northern Yellowstone area--Gray to brown shale and siltstone; north and south Wyoming--Dull-gray shale, gray siltstone, and fine-grained gray sandstone.

Lithology: shale; siltstone; sandstone

Coalmont Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area

COALMONT FORMATION (EOCENE AND PALEOCENE)--Tan to gray arkosic micaceous soft sandstone, claystone, and locally derived conglomerate.

Lithology: medium-grained mixed clastic; fine-grained mixed clastic; conglomerate

Mesozoic and Paleozoic rocks (Phanerozoic | Paleozoic Mesozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian(?) Triassic(?) Jurassic(?) Cretaceous-Late) at surface, covers 0.1 % of this area

MESOZOIC AND PALEOZOIC ROCKS (north Wyoming). Shown in small areas of complex structure. East Flank of Absaroka Range--Dinwoody Formation, Phosphoria Formation and related rocks., Tensleep Sandstone, and Amsden Formation (Lower Triassic through Upper Mississippian). East flank of Bighorn Mountains--Cloverly, Morrison, Sundance, Gypsum Spring, Chugwater and Gypsum Spring Formations (Lower Cretaceous through Permian). MESOZOIC AND PALEOZOIC ROCKS (south Wyoming). Shown in small areas of complex structure. South side of Granite Mountains north of Green Mountain--Nugget Sandstone, Chugwater and Goose Egg Formations, Tensleep Sandstone, and Amsden Formation (Jurassic? through Upper Mississippian). South flank of Ferris Mountains--Nugget Sandstone and Chugwater and Goose Egg Formation (Jurassic? through Permian). Northeast flank of Seminoe Mountians--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations (Lower Cretaceous through Permain). West flank of Sierra Madre--Chugwater, Goose Egg, Casper, and Fountain Formations (Upper Triassic through Middle Pennsylvanian). East Flank of Laramie Mountains--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations, and, east of fault in T. 19 N., Casper Formation (Lower Creatceous through Middle Pennsylvanian). NUGGET SANDSTONE in south--Gray to dull-red, massive to coarsely crossbedded quartz sandstone.

Lithology: sedimentary rock; clastic; mixed clastic/volcanic; mixed clastic/carbonate

Metamorphosed mafic and ultramafic rocks (Archean) at surface, covers 0.2 % of this area

METAMORPHOSED MAFIC AND ULTRAMAFIC ROCKS. Teton Range--Rendezvous Metagabbro; 2,875 Ma or older. Gros Ventre Range--Hornblende gneiss and serpentinite. Wind River Range--Pillowed amphibolite, metagabbro, and ultramafic sills. Wind River Canyon (cutting through Owl Creek Mountains)--Amphibolite and felsic gneiss of volcanic origin. Older than 2,700 Ma. Bighorn and Granite Mountains--Amphibolite. Seminoe Mountains--Amphibolite of volcanic origin, komatiite, and metagabbro. Casper Mountain--Amphibolite and serpentinite. Laramie Mountains--Amphibolite of volcanic origin, komatiite(?), metagabbro, and ultramafic sills.

Lithology: metavolcanic rock

Chugwater and Goose Egg Formations (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers 0.3 % of this area

CHUGWATER AND GOOSE EGG FORMATIONS (north Wyoming). CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone; CHUGWATER FORMATION OR GROUP (south Wyoming)--Red shale and siltstone containing thin gypsum partings near base. Group includes Popo Agie Formation (red shale and red, yellow, and purple siltstone; lenses of lime-pellet conglomerate), Crow Mountain Sandstone (red and gray, thick bedded), Alcova Limestone, and Red Peak Formation (red siltstone and shale). Chugwater Formation includes as members all the units listed above. Includes overlying Jelm Formation in Shirley and Seminoe Mountains and at northern end of Laramie Basin. JELM FORMATION--Red sandstone. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.

Lithology: siltstone; sandstone; shale; conglomerate; evaporite; dolostone (dolomite); limestone